Method and means for producing colored photographic images



Patented Mar. 18, 1947 METHOD AND MEANS FOR PRODUCING COLORED PHOTOGRAPHIC IMAGES Henry T. Neumann, New York, N. Y., assignor to Spectrum Products Company, Inc., New York, N. Y., a corporation of New York No Drawing. Application September 23, 1940, Serial No. 357,830

Claims.

The invention relates to a method and means for producing a colored photographic'image.

One of the objects of my invention is to provide a highly improved method and means for producing a colored photographic image which is characterized by its intense color and freedom from stains.

Another object of my invention is to provide a photographic developer for colored images which has a stabilizing agent to prevent deterioration of the coupler when in solution.

Another object of my invention is to provide a photographic developer of the character described which will be economical to manufacture, extremely simple to employ, and which shall be highly efficient for the purposes set forth.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

In accordance with my invention, three separate mixtures of dry compounds are prepared. The first of these mixtures comprises a rapid silver halide reducer such as monomethylparaaminophenolsulphate (sold under the trademark metol), a preservative such as sodium sulphite, and a standard coupling inducing silver halide reducer such as para-aminodimethylanalinmonohydro-,

chloride. I have found that by employing a rapid reducing agent, I have succeeded in obtaining colors more intense than those hitherto produced when only a standard coupling inducing reducer was employed. The use of an extremely rapid reducing agent, such as metol, is believed to accomplish this result due to the greater amnity which the coupler appears to have for the reduced silver when the latter is present in large.

amounts, as contrasted with the slower and less complete action of the coupler with silver when the silver is reduced slowly over a protracted period of time. 7

The secondmixture comprises a standard accel'erator, such as borax or sodium carbonate, and the combination of an additional stronger accelerator, such as for example sodium hydroxide, together with a gelatin hardening agent, comprisins an alkali metal sulphate such as sodium sulphate. The use of the combined strong accelerator and hardener has been found to prevent staining of the clear portions of the film and-to provide a sharp outline for the photographed ob jects. Such action is thought to be brought about by the creation'of minute pores over the surface of the film through which the rapidreducer, coupling inducing reducer and coupler act upon the latent image. Under these conditions, the unexposed silver halide is not reduced and coupled as speedily as the latent image, and a substantial period of time elapses between complete development of the latent image and the first appearance of a fog or stain. It is thus easily possible to stop development after the latent image has been brought out and before any stains are produced.

This method and means is to be contrasted with that presently used in color developing, wherein only standard accelerators are employed. These accelerators open relatively large pores on the surface of the film throughwhich the rapid reducer, coupling. inducing reducer and coupler act with almost equal speeds upon the latent image and on the unexposed portions of the film, so that a stain is produced a short time after or simultaneously with the development of the latent image.

The third or coupling mixture comprises a standard coupler and sodium sulphite. At the present time these couplers, when brought into solution prior to being used in color developing, are subject to very rapid deterioration due to the presence of adsorbed oxygen. The time over which such a coupling solution remains stable and eiiective varies from an extremely short period of about thirty seconds to a maximum period of about ten minutes. It is thus apparent that a coupler prepared according to such method can only be used immediately after the solution is formed and is therefore not susceptible of easy or economical application.

In accordance with my invention, I stabilize the coupler in solution by employing in the third mixture a nonoxidizing compound which will impart to the solution a pH of from four to six.

, This compound is believed to act as a buffer and maintain the pH in the aforementioned range, to thus prevent deterioration by oxidation of the coupler. I have found that thefollowing compounds will give satisfactory solutions: tartaric acid, citric acid, and mono-basic sodium acid phosphate.

Coupling solutions prepared with mono-basic sodium acid phosphate have been found to remain stable and to give satisfactory results over periods as long as four months.

To employ these three mixtures in developing a colored image, they are each separately added to water in order to provide three aqueous solutions, an organic solvent such as propyl alcohol being added to the third mixture to dissolve the coupler before introducing the third mixture in water.

Immediately prior to developing, these solutions are mixed together and applied tothe, film in any manner well known in the art, as by submerging a film therein. Subsequent to developing, the film may be washed, fixed and then washed again in the usual manner.

The following is a specific example of each of three mixtures which I have found give highly satisfactory results, it being understood that this example is in no way limitative:

Mixture A (reducing and coupling inducing mixture) -Qre Metol 1 Sodium sulphite 15 Para aminodi'methylanalinrnonohydrpghlo; ride 3 Mixture B (accelerating and hardening mixture) Grams Borax 6 Sodium hydroxide 4 9d m.$. e 40 M iscture C (couplingmimture) Grams Par'a-nitrophenylacetonitrile A 1 Sodium'. acid phosphate (mono-basic) 1 Sodium sulphite 5 The mixturesare added to water in the following proportionsr2' gramsMixture'A'to 100 cc. of water to form solution A; 2 grams Mixture B to 100 cc. of water toform solution B; and 1 gram Mixture Cto 100 cc. of water to form solution C. From the solutions thus prepared I mix 18 cc. of'solutionA, 9 00. of solution B, cc. of solutionC and 300 cc. ofwater to form the ultimate .developingsolution. If desired, 6 drops of potassium bromide may also be added to prevent fogging.

The usev of the coupler above set forth will produce a redtimage; However, any other coupler for producing a'color other than red may be employed 'without'departing from the spirit of my invention.

1: It will thus beiseen' that there is provided a 'rnethod and means'of which the several objects of this inventionare achieved, and which are well adapted'to meet the conditions of practical use. As various possible embodiments might be made of theabovet'invention, and as various changes might'beLmade in. theembodiments above set forth,'it is to be-understood'that all matter herein setforthis to be interpreted as illustrative and .not in alimiting sense.

" .Havingthus described my invention, I claim as new and desire to secure by Letters Patent:

1. A photographic color developer comprising a coupling inducing'silver halide reducer, a strong acce1erator,'.an alkali metal sulphate, a non-sil ver-halideer'educing coupler, a non-oxidizing buffer whose, aqueous solution has a pH of from four tojsix, and a rapid silver halide reducing color intensifying agent of such nature as not to affect the color forming capacity of 'said developer.

7 2. A photographic color developer comprising "meto, a coupling inducing silver halide reducer, an accelerator, and a coupler.

"3. An alkaline photographic color developer solution comprising a coupling inducing silver "halide'reducer', a non-silver-halide-reducing cou- 'plr, and' a non-oxidizing bufrerqwncse aqueous 'soliition hasa 'pH rrq'mrburjte six. f

A ph"otographiccolor developer comprising a coupling"iridiicingsilver Halide reduci'fs o dium hydroxide, s"odiur n sulphate, :a maneuver-handere'ducin'g coupler, and sodium acid "phosphate.

5. A method of color developing latent images on a silver halide film comprising treatin said film with a solution including metol, a coupling inducing silver halide reducer, an accelerator and a coupler.

6. A method of color developing latent images on a silver halide film comprising treating said film with a solution including metol, a coupling inducing silver halide reducer, sodium hydroxide, sodium sulphate, a non-silver-halide-reducing coupler, and mono-basic sodium acid phosphate.

7. A stock coupling solution which is adapted tobe added to an alkaline photographic coloring developing solution, said stock coupling solution comprising water, a non-silver-halide-reducing coupler, and an acidic bufiing reagent for preventing rapid deterioration of said coupler while in solution in water, said reagent consisting of a non-oxidizing soluble substance whose aqueous solution has a pH of from four to siX.

A stock :coupling solution which is adapted to be added to an alkaline photographic coloring developing solution, said stock coupling solution comprising water, a non-silver-halide-reducing coupler; and an acidic buffing reagent for preventing rapid deterioration of said coupler while in solution in water, said reagent consisting of mono-basic sodium acid phosphate.

'9. A photographic color developer comprising a coupling-inducing silver halide reducer, an accelerator, a coupler, and a rapid silver halide reducing color intensifying aminophenol.

10. A method of color developing latent images on a silver halide film comprising treating said film with a solution including a coupling inducing silver halidereducer, an accelerator, a coupler, and a rapid silver halide reducing color intensifying aminophenol.

- HENRY T. NEUMANN.

REFERENCES CITED The following references are of record in the file'of this patent:

UNITED STATES PATENTS OTHER REFERENCES Famulener, Some studies on the use of color coupling developers for toning processes, Journal of the Society of Motion Picture Engineers,

vol. 32, April 1939, DD. 412-418, pa e 416 cited. (Copy in Div. 7.)

Gifford, A Long'keeping Developer, Photographic Journal, London, May 1923, page 239.

Giijford, Monthly Abstract Bulletin, issued by Kodak Research Laboratories, vol. IX, No. 7, July rezap e 227." 7

(Copies of'the last two publications are in the Scientific Library.) 

